What role do plant-fungal mutualisms play in restoration ecology? Assessing the impacts of coastal dune modification on mycorrhizae, and whether reconnecting mycorrhizal networks can facilitate restoration of dune vegetation.
School of Earth & Environmental Science
Thompson, Eilysh R., What role do plant-fungal mutualisms play in restoration ecology? Assessing the impacts of coastal dune modification on mycorrhizae, and whether reconnecting mycorrhizal networks can facilitate restoration of dune vegetation., BEnviSci Hons, School of Earth & Environmental Science, University of Wollongong, 2015.
Background - Anthropogenic landscape modification, through such processes as deforestation, agricultural and urban expansion, significantly threatens biodiversity and ecosystem function by disrupting species interactions, particularly mutualisms. Whilst the effects of landscape change on other mutualisms, such as pollination, have been well studied, relatively little is known about impacts on the mutualistic association between plants and mycorrhizal fungi within the soil. Plant-mycorrhizal associations occur in all terrestrial ecosystems, for approximately 80 % of all known terrestrial plant species, and are fundamental to the ecological function and diversity of vegetation communities. Disruption of plant-mycorrhizal mutualisms could thus drive a reduction in biodiversity across modified landscapes, and prevent the recovery of plant communities in response to restoration intervention by land managers.
Aims - The first aim of this study was to determine whether the abundance and functional identity of fungi within native plant roots vary between reconstructed and remnant coastal dune habitats, using a comparative field-based study within the Illawarra region of southern New South Wales. The second aim was to assess whether the application of a mycorrhizal inoculate (obtained from remnant dunes) to nurserygrown plants prior to their introduction to reconstructed dunes facilitates their establishment and enhances vegetation recovery, through both field and mesocosmbased experiments.
Study system – Since European colonisation of the Illawarra region approximately 200 years ago, the landscape has been extensively modified through removal of coastal vegetation for agriculture and urbanisation. Since the 1980s and early 1990s, many of the coastal dunes were reconstructed by local land managers through the deposition of sand from nearby mines and reintroduction of native vegetation, in order to limit coastal erosion, protect urban assets from destructive storms and wave surges, and restore the native coastal ecosystems. The ecological function of these reconstructed dunes relative to those in which the native vegetation was not destroyed by European settlement is not known.
Results - For the field-based study I found that there were no significant differences in the abundance and composition of fungal structures between plants on reconstructed and remnant coastal dune habitats. Rates of mycorrhizal colonisation of plant roots varies substantially across the coastal landscapes, but was not influenced by the history of disturbance of the dune vegetation. In the mesocom experiment, there was a non-significant trend towards increased growth of native plant seedlings in response to mycorrhizal inoculation. However, in the field experiments, I detected significant positive effects of inoculate addition on survivorship of native seedlings, although this depended upon the identity of the plant species. Inoculation had no effect on Lomandra longifolia survival, with all plants surviving, whilst inoculation moderately improved survival rates of the grass Poa labillardieri.
Study outcomes and implications – My study has demonstrated that mycorrhizal associations between plants and their fungal mutualists may not always be adversely affected by habitat disturbance and subsequent reconstruction. Furthermore, inoculating seedlings with additional mycorrhizae is unlikely to significantly increase rates of vegetation restoration at reconstructed dunes in the short-term. It is probable that mycorrhizae were either not impacted by the original deforestation of the coastal dunes or were able to rapidly recolonise the dune when it was rehabilitated and reform functional networks with the reintroduced plants. I observed, however, that coastal plant communities are still highly fragmented and degraded by a variety of disturbance processes, including alien plant invasion, vandalism and attack by vertebrate pests, such as rabbits. It is suggested that future research investigate the incidence and magnitude of these disturbances between remnant and reconstructed dunes, what their impacts are on native vegetation restoration, and the mechanisms by which these impacts can be reduced.